Mastering PCB Design: Best Practices for Developing Accurate and Reliable Component Libraries

Over many years, I have seen many elaborate PCB Library systems. The best ones were not based on the size, but rather on the quality of the information. The old axiom is “not Quantity but rather Quality.” 

I recently sat with a VP of Engineering, and I asked what he thought of his PCB Library. He thought for a moment and said, “I believe it is pretty good.” I asked my question another way, “But do you know?” There is a difference. If I tell you that touching the burner of a hot stove is going to burn you, at that point, you only believe it. Now, if you go and feel the hot stove and it burns your hand, what just happened? You went from believing to knowing. 

With an industry that demands perfection, it is not good enough to just “believe” that your library is good enough. You must KNOW! But really, what is good enough? What is that? Well, we got the board through Fab and Assembly, and maybe it went through some compliance checks. So, it must mean that it is correct, right? No, it could be that you were just lucky.

Off the coast of a somewhat rugged area of North Carolina, there stand three Lighthouses.

Being such a harsh area for naval vessels, it is a well-known area for shipwrecks. Contrary to belief though, a ship captain, when he is coming into port, will not go from lighthouse to lighthouse. Instead, he lines up all three lighthouses so that he only sees a single light. In much the same way, we are verifying that all the lighthouses are lined up and that we see only a single light during the component auditing process or review. Simple rule: if you see more than one light, something is wrong.

Verification Vs Validation

Most people use these terms interchangeably on a regular basis, losing the true meaning of each. I must admit, there are subtle differences between them, but when we apply them to our library, the definitions become very clear. Verification is establishing the truth or accuracy of something. Meanwhile, validation is checking or proving the quality of being logically or factually sound; verifying the cogency or accuracy of something. 

The review process verifies if what is represented in the library is true. Does it line up with the Standard? What standard to use? Validation determines if the information is factually sound. 

Our last two pillars of Reliability and Traceability, both are parts of the audit process used to verify and validate library information. The Reliability pillar Verifies the process while Traceability validates the data. 

The Verification Standard

A successful verification process must be established on a known standard. What do I mean by standard? It is the benchmark to match the data against. As mentioned earlier: the truth.  

The Datasheet

The first verification document is the Datasheet. It is usually the very first document engineers and librarians go after. If the process does not start there, we will be setting ourselves up for major problems down the road. 

But (and that is a big but), some datasheets are wrong. Because people trust a single datasheet way too much; the problems with these datasheets usually end up on PCB Designs, hidden until Assembly. Before you know it, you are making that long walk to the manager’s office. 

When this happens, and at some point, in your career, it will happen, document it. If you find such a problem, it could become a habit for that vendor. No company can afford to fact-check datasheets and Components by running PCB board runs. You should consider dropping them from your preferred vendor list. At least red-flag them. You caught a problem that may exist in other parts they provide. 

Another strategy is to have multiple suppliers for any components in a design. First, this provides us with an alternate part in case our first choice falls through for some reason. It also gives another datasheet to compare the component against. If you work with multiple manufacturers, you should pull every datasheet to determine if anything is out of line — Lining up those lighthouses and comparing and determining what we see. 

IPC Standards

Fortunately, we are not left to our own devices to determine if a component or a datasheet is correct. The Institute for Interconnecting and Packaging Electronic Circuits (IPC) released several standards we could use.  The IPC is the leading authority in the Printed Circuit Board industry since its founding in 1957. I have never read an IPC standard I did not like. The criteria that would help in the review process are the Design & Land Pattern category. They are IPC-2221, IPC-2222, IPC-2223, IPC-7351C (Surface mount components), IPC-7251 (Through Hole Components).

I would highly recommend using IPC standards as the foundation of your custom PCB component libraries. 

IPC-7351 and IPC-7251 give very detailed component breakdowns with the specific naming convention we discussed earlier. 

Through Standards Developing Organizations (SDOs), the standards are regularly reviewed and updated to align with changes in the industry. Although this falls a bit under the Tailored pillar, they are an excellent way to know if changes to the standards affect any of your library models. For example, a recent release of IPC-7351C changed the shape of any rectangular pad to round corners. The IPC made this change to facilitate 45-degree angle trace routing because the sharp turns act as antennas.

A good Library system with a solid second pillar (Managed) will have the characteristic that whenever changes occur, the lifecycle automatically changes to a “new” state. That way any changes in the standard will identify changes in the custom PCB component libraries. 

Quarantine “New” Components

If you did not do this already, you should establish the guideline that no PCB will release or fabricated with any components in a “New” state. You can create a separate folder to quarantine these components. Until you finish the audit, those components should not be trusted or used in released designs. 

Follow the golden rule of Reliability. The person who did the work cannot review it. The vital importance is to get another set of eyes to look at the custom PCB component libraries—this is important because the person who did the work has a subjective view instead of an objective one. Therefore, your best bet is to have a few people act as the review board that verifies and documents the new components... 

Altium and the Fourth Pillar: Reliability

Altium has several available tools for the Review Process. 

Component Design Rule Checks 

The structure of the library is only as strong as its smallest part, the component. The release of Altium 18 made a new feature available for conducting Design Rule Checks on the Component Level. 

There are three categories of checks. 

• Violations Associated with Components

• Violations associated with Footprints 

• Violations associated with Symbols. 

From the very moment a component is placed, Altium Designer checks the library. These checks standardize the component creation process. Ultimately, this standard for component-level quality feeds into the quality of the PCB designs.

Item Manager

Another important tool is the Item Manager. As you will recall, the Item Manager does multiple things for us.

1. Runs a check of the Component Source 
2. Verifies whether the present status is in sync with the Library
3. Verifies the Lifecycle of the component (the concern is with those that have not been checked and Released) 

Workflows

Altium Concord Pro^® is one of the most exciting things that Altium has put out for many years. With the addition of control of the data (Libraries), the other side of the coin is the control of the process. I would highly recommend looking into it right away. What Concord Pro does, is provide the ability to determine if a Component of a specific Lifecycle will be allowed to be used on a design. If any component has a NEW condition, then the Component Error message will be “That the Model Revision is in an Inapplicable State.”

Practical Steps

• Identify those standards by which the PCB library will be measured. 
• Identify the components in your library that have a single source and flag those components.
• Obtain the basic IPC standards of IPC-2221, IPC-2222, IPC-2223, IPC-7351C & IPC-7251
• Setup a location to place the new Component for the Review Board Audit
• If a Review Board does not exist, set one up.  

Need more information? Talk to an Altium expert today to learn more and discover Altium Concord Pro^™ a unified data and product lifecycle management platform that integrates with Altium Designer^® and other mechanical design tools.